A 1.4-NM GOLD CLUSTER COVALENTLY ATTACHED TO ANTIBODIES IMPROVES IMMUNOLABELING

A large gold cluster (Au1.4nm) was covalently coupled to IgG and Fab' fragments. Its gold core is 1.4 nm in diameter and the Fab'-Au1.4nm immunoconjugate is the smallest gold immunoprobe that can be seen directly in the conventional electron microscope. It is useful in high-resolution immunolabeling, providing a resolution of 7.0 nm. The cluster's visibilitY can be enhanced with silver development for use in EM or light microscopy for histological purposes, or to detect less-than-or-equal-to 0.2 pg of antigen in immunoblots. By using a gold compound with covalent attachment, a number of advantages over colloidal gold probes are realized, including better resolution, stability, uniformity, sensitivity, and complete absence of aggregation; its small size should also improve penetration and more quantitative labeling of antigenic sites.